the separating semi-colon shows up on a continuation line (legal, but
weird).
Bug reported and fixed by Matthew Cowles. Test case and sample email
included.
get_type(): Use a compiled regular expression, which can be shared.
_get_params_preserve(): A helper method which extracts the header's
parameter list preserving value quoting. I'm not sure that this
needs to be a public method. It's necessary because we want
get_param() and friends to return the unquoted parameter value,
however we want the quote-preserved form for set_boundary().
get_params(), get_param(), set_boundary(): Implement in terms of
_get_params_preserve().
walk(): Yield ourself first, then recurse over our subparts (if any).
<http://sf.net/projects/mimelib>. There /are/ API differences between
mimelib and email, but most of the implementations are shared (except
where cool Py2.2 stuff like generators are used).